Are We Experiencing a Mass Extinction of the Skin Microbiome?

The skin microbiome The skin microbiome is a poorly understood yet important part of human physiology, encompassing the bacteria, yeast, fungi, and viruses that colonize every skin surface. Microecosystems within the skin microbiome are found in the nasal passages, lungs, throat, and vagina; however, most bacteria reside in the gastrointestinal tract. The skin harbors 10 of the 12 bacteria and is the second most populous site. It is thought that stress, age, diet, chemical exposure, access to health care, and lifestyle all influence the skin microbiome. There are trillions of organisms on the human body, such that 43% of the human cell count belongs to the microbiome, making it an aspect of health that cannot be overlooked.

Amazingly, our skin microbiome is going extinct, an event labeled catastrophic biodiversity loss. This event is thought to be due to a modern lifestyle, antibiotics in foods, and a Western diet. Identification of large shifts in the microbiome has been enabled by shotgun metagenomic sequencing, which has enabled more precise characterization of the skin microbiome influenced by sebum and sweat on the skin surface. Abnormalities in the skin microbiome, termed dysbiosis, can result from a loss of microbial diversity, an increase in pathogenic organisms, or a loss of beneficial organisms. Challenges exist to address this issue, however, since there are no concrete guidelines for what constitutes a normal skin microbiome. It has been established that healthy skin possesses much more microbial biodiversity than diseased skin.

It is estimated that the skin microbiome of the developed world has a 30% to 84% reduction in biodiversity compared with that of indigenous peoples and individuals living in a rural environment.1 This is theorized to be due to soaps, cosmetics, detergents, antibiotics, pollution, and cleaning products. A modern lifestyle of living in isolation from nature in a hypersanitized environment also contributes. Cosmetics and skin care products are typically formulated at an acidic pH of 5, which can alter the microbiome. Soaps and detergents have a more alkaline pH, which also damages the microbiome. It is thought that the explosion in skin care product and cleanser use led to a 400% increase in eczema in the UK from 1946 to 2011.

Dysbiosis is characteristic of many skin diseases, including acne, atopic dermatitis, eczema, seborrheic dermatitis, tinea pedis, rosacea, psoriasis, and hidradenitis suppurativa. A link between early-life antibiotic administration and atopic dermatitis may be caused by dysbiosis. Dysbiosis may also be present in cardiovascular disease, diabetes, schizophrenia, Parkinson disease, and Alzheimer disease. It appears that skin dysbiosis also correlates with gut dysbiosis. Some now believe that improvement in atopic dermatitis is not related to a decrease in Staphylococcus aureus on the skin surface, but rather to an increase in skin microbiome biodiversity. Others believe that the low-grade chronic inflammation induced by cutaneous Malassezia overgrowth can trigger neurodegenerative issues, such as Parkinson disease. This is an interesting thought, since seborrheic dermatitis induced by Malassezia is commonly found in patients with Parkinson disease.

The microbiome is the first line of defense in skin infections, and diversity is the key to microbiome health. Topical probiotics have been somewhat controversial but may hold unrealized promise for treating chronic skin diseases with poorly understood pathophysiology. As dermatologists, we are microbiome experts, and correcting dysbiosis is part of our therapeutic goal.

Zoe Diana Draelos, MD, is a clinical faculty member in the Department of Dermatology at Duke University School of Medicine in Durham, North Carolina; president of Dermatology Consulting Services in High Point, North Carolina; and Dermatology Times’ editor in chief emeritus.

Reference

1. Wallen-Russell C, Pearlman N, Wallen-Russell S, Cretoiu D, Thompson DC, Voinea SC. A catastrophic biodiversity loss in the environment is being replicated on the skin microbiome: is this a major contributor to the chronic disease epidemic? Microorganisms. 2023;11(11):2784. doi:10.3390/microorganisms11112784